The role of coronary thrombosis in myocardial infarction: further evidence shown by intracoronary thrombolysis with streptokinase.

Myocardial infarction is usually caused by a thrombus occurring on a significant coronary lesion. A 60-year-old male was admitted with an acute evolving anterior myocardial infarction. Three hours after the beginning of chest pain, the electrocardiogram showed ST-segment elevation in the anterior and lateral leads which persisted despite intravenous nitroglycerin (100 mcg/min). One hour later, an angiogram showed complete obstruction at the origin of the left anterior descending artery (LAD). After intracoronary streptokinase (250,000 units) the LAD opened and a 90% obstruction was seen at its origin. However, an anterior myocardial infarction occurred. One month later, an angiogram showed a slight irregularity at the origin of the LAD. Thus, this case demonstrates that 1) a myocardial infarction may occur with a near normal coronary artery, and 2) a thrombus may occur at the site of a slight coronary irregularity.